Method for determining the degree of elongation of rolled magnetic metal strips and an apparatus for the same

ABSTRACT

A method for determining the degree of elongation of rolled magnetic metal strips and an apparatus for the same which comprises bringing automatic induction detectors close to one side of a travelling rolled magnetic metal strip to cause changes with time in the displacement of the metal strip in the direction of its thickness to be detected in the form of changes in inductance, supplying outputs from the detectors to one side of an AC bridge circuit, demodulating outputs from the bridge circuit by a demodulator, differentiating the values of the demodulated outputs by differentiators, and squaring the differentiated values by square-law circuits, and detecting the momentary values of the degrees of elongation of said metal strip, thereby controlling its rolled form.



1. A method for determining the degree of elongation of rolled magnetic metal strips which comprises the process of detecting electrical signals representing variations in inductance corresponding to changes with time in the displacement of a rolled magnetic metal strip in the direction of its thickness while it is travelling, differentiating the detected signals and squaring the differentiated outputs to obtain the momentary values of the degrees of elongation of the metal strip, whereby the squared outputs can be used as signals for controlling the form of the metal strip.
 2. A method for determining the degree of elongation according to claim 1 wherein the detecting process comprises those of detecting by induction detectors changes with time in the displacement of the magnetic metal strip in the direction of its thickness in the form of variations in inductance, supplying outputs from the detectors to an AC bridge circuit and demodulating outputs from said AC bridge circuit.
 3. A method for determining the degree of elongation according to claim 1 which consists in detecting electrical signals representing variations in inductance corresponding to changes with time in the displacement of the magnetic metal strip in the direction of its thickness at several points in the transverse direction of the metal strip and differentiating and squaring each of these electrical signals.
 4. An apparatus for determining the degree of elongation of rolled magnetic metal strips which comprises means for detecting electrical signals represeNting variations in inductance corresponding to changes with time in the displacement of the metal strip in the direction of its thickness while it is travelling a circuit for differentiating the detected electrical signals and a square-law circuit for squaring the differentiated outputs to obtain signals representing the momentary values of the degrees of elongation of the metal strip whereby the squared outputs can be used as signals for controlling the form of the metal strip.
 5. An apparatus for determining the degree of elongation according to claim 4 wherein the detecting means comprise induction detectors disposed in close proximity to one side of the magnetic metal strip, an AC bridge circuit supplied with outputs from the detectors and a circuit for demodulating outputs from the AC bridge circuit.
 6. An apparatus for determining the degree of elongation according to claim 4 wherein there are juxtaposed a plurality of automatic induction detectors in the transverse direction of the metal strip and outputs from the detectors are supplied to a plurality of differentiation and squaring circuits. 